drm/i915: Add per ctx batchbuffer wa for timestamp
Restoration of a previous timestamp can collide with updating the timestamp, causing a value corruption. Combat this issue by using indirect ctx bb to modify the context image during restoring process. We can preload value into scratch register. From which we then do the actual write with LRR. LRR is faster and thus less error prone as probability of race drops. v2: tidying (Chris) v3: lrr for all engines v4: grp v5: reg bit v6: wa_bb_offset, virtual engines (Chris) References: HSDES#16010904313 Testcase: igt/i915_selftest/gt_lrc Suggested-by:Joseph Koston <joseph.koston@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by:
Mika Kuoppala <mika.kuoppala@linux.intel.com> Acked-by:
Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by:
Chris Wilson <chris@chris-wilson.co.uk> Link: https://patchwork.freedesktop.org/patch/msgid/20200424230546.30271-1-mika.kuoppala@linux.intel.com
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